Exhaust system having parallel asymmetric turbochargers and EGR

Abstract

An exhaust system for a use with a combustion engine is provided. The exhaust system may have a first exhaust manifold configured to receive exhaust from the engine, and a first turbocharger driven by exhaust from the first exhaust manifold. The exhaust system may also have a second exhaust manifold configured to receive exhaust from the engine in parallel with the first exhaust manifold, and a second turbocharger driven by exhaust from the second exhaust manifold and having a different flow capacity than the first turbocharger. The exhaust system may further have an exhaust gas recirculation circuit in fluid communication with the second exhaust manifold.

1. An exhaust system for an engine, comprising:
 a first exhaust manifold configured to receive exhaust from the engine; 
 a first turbocharger driven by exhaust from the first exhaust manifold; 
 a second exhaust manifold configured to receive exhaust from the engine in parallel with the first exhaust manifold; 
 a second turbocharger driven by exhaust from the second exhaust manifold and having a different flow capacity than the first turbocharger; 
 a balancing valve upstream of the first and second turbochargers; and 
 an exhaust gas recirculation circuit initiating upstream of the balancing valve from only a single exhaust line, the single exhaust line extending from the second exhaust manifold. 
 
     
     
       2. The exhaust system of  claim 1 , further including,
 a passageway connecting the first and second exhaust manifolds, 
 the balancing valve being located within the passageway to selectively restrict a flow of exhaust through the passageway. 
 
     
     
       3. The exhaust system of  claim 2 , further including a control valve located within the exhaust gas recirculation circuit to regulate a flow of exhaust directed through the exhaust gas recirculation circuit. 
     
     
       4. The exhaust system of  claim 3 , further including a check valve located within the exhaust gas recirculation circuit to provide for a unidirectional flow of exhaust through the exhaust gas recirculation circuit. 
     
     
       5. The exhaust system of  claim 4 , wherein the check valve is located downstream of the control valve at a location where exhaust mixes with inlet air. 
     
     
       6. The exhaust system of  claim 3 , further including a cooler located within the exhaust gas recirculation circuit upstream of the control valve. 
     
     
       7. The exhaust system of  claim 6 , further including:
 a flow sensor located downstream of the cooler; and 
 a controller in communication with the flow sensor, the control valve, and the balancing valve, the controller being configured to regulate operation of the control valve and the balancing valve in response to input from the flow sensor. 
 
     
     
       8. The exhaust system of  claim 7 , wherein the flow sensor is located upstream of the control valve. 
     
     
       9. The exhaust system of  claim 1 , wherein the exhaust gas recirculation circuit is in fluid communication with only the second exhaust manifold. 
     
     
       10. A method of handling exhaust from an engine, comprising:
 receiving exhaust from a first plurality of combustion chambers; 
 removing energy from exhaust received from the first plurality of combustion chambers; 
 receiving exhaust from a second plurality of combustion chambers; 
 directing a portion of the exhaust received from the second plurality of combustion chambers through an EGR circuit back into the engine for subsequent combustion; the EGR circuit initiating upstream of a balance valve from only a single exhaust line, the single exhaust line extending from the second plurality of combustion chambers; 
 removing energy from a remaining portion of the exhaust received from the second plurality of combustion chambers in parallel with removing energy from the exhaust received from the first plurality of combustion chambers, 
 wherein removing energy from the remaining portion of the exhaust increases a pressure of the exhaust received from the second plurality of combustion chambers by an amount greater than a pressure increase of the exhaust received from the first plurality of combustion chambers caused by removing energy; 
 sensing a flow rate of the portion of the exhaust directed back into the engine; and 
 adjusting a restriction placed on a flow of the exhaust received from the second plurality of combustion chambers based on the sensed flow rate. 
 
     
     
       11. The method of  claim 10 , wherein the pressure increase of the exhaust received from the second plurality of combustion chambers forces exhaust to flow from the second plurality of combustion chambers back into the engine. 
     
     
       12. The method of  claim 11 , further including selectively passing exhaust received from the second plurality of combustion chambers to mix with exhaust received from the first plurality of combustion chambers before removing energy, wherein the selective passing reduces an amount of exhaust directed back into the engine. 
     
     
       13. The method of  claim 10 , further including selectively restricting the portion of the exhaust directed back into the engine. 
     
     
       14. The method of  claim 13 , further including inhibiting bidirectional flows of the portion of the exhaust directed back into the engine. 
     
     
       15. The method of  claim 13 , further including cooling the portion of the exhaust directed back to the engine before the portion of the exhaust is selectively restricted. 
     
     
       16. The method of  claim 15 , further including,
 adjusting the restriction of the portion of the exhaust directed back into the engine based on the sensed flow rate. 
 
     
     
       17. The method of  claim 16 , wherein the restriction of the exhaust received from the second plurality of combustion chambers is adjusted to a fullest extent possible before the restriction of the portion of the exhaust directed back into the engine is adjusted. 
     
     
       18. A power system, comprising:
 a combustion engine having a first plurality of combustion chambers and a second plurality of combustion chambers; 
 a first exhaust manifold configured to receive exhaust from the combustion engine; 
 a first turbocharger driven by exhaust from the first exhaust manifold; 
 a second exhaust manifold configured to receive exhaust from the combustion engine in parallel with the first exhaust manifold; 
 a second turbocharger driven by exhaust from the second exhaust manifold and having a lower flow capacity than the first turbocharger; 
 an exhaust gas recirculation circuit in fluid communication with the second exhaust manifold; 
 a passageway connecting the first and second exhaust manifolds; 
 a balancing valve located within the passageway to selectively restrict a flow of exhaust through the passageway; and 
 a control valve located within the exhaust gas recirculation circuit to regulate a flow of exhaust directed through the exhaust gas recirculation circuit. 
 
     
     
       19. The power system of  claim 18 , wherein the exhaust gas recirculation circuit initiates upstream of the second turbocharger.